Control mechanism



P 1932- I c. B, CAMPBELL 1,875,326

CONTROL MECHANISM Filed July 9. 1950 as 61 ea H95 7' SECOND F/ SECONDFLU/D FLU/D FL U/D FLU/D PEA-$5025 C. 5. Campbell.

ATTORNEY Patented Sept. 6, 1932 can an; 1212s BATE am" .cmnnnon B.oAMrnELn'or. MooREs, PENNSYLVANIA, essmnoa'ro wns'rmcnousn ELECTRIC; &.mnnrncrnnme. COMPANY, Aloolmonmmn 0.1? BENNSXLVAHIA oonrxor; r nonnnrsmApplication filed Jul -9,- 193m- Serialf ito; 466,797.

Mjy. invontio1r-relzltes to as; control mechar: nism for a prime movermore particularlyto control; mechanism I fora multi-stage elastic fluid.prime: mover having: openings two or, more;intermediate-pressure:-stagesfor extracting-partially expanded 1110lJlV8- fluidifromthe.PIiHIGi-HIOVGIT'IOIL fonadmitting. motive fiuid:thereto,-.and it'hasforitseobJect:

to provide an .iinprcvediconstnuction off such.

mechanism.

A more particular object is to provide an improved: controlmechanismofzthe character: set forth .1 which w-ilhup on change in,demand for flow of fluid through oneof; the openings, operate the valvemeans at, said; one opening'toefi'ect the desired? change in flow and tomaintain; the. desired pressure, and which will? at; the sametime;operate the ad;-- mission valve and. the valve: means at tho- 51ozotheropening to maintain: the proper.- load on.

Still the prime mover and thepnopen' flow and. pressure at: said otheropenings.

In accordance with my invention, I pro vide a: control deviceassociated: with: each opening which provides two, fluid: pressuresvarying'inopposit'e' directions to each other in response to. variationsin: pressure at. the opening; A regulating means/for control--ling-the'fiow at eachiopeningxis responsive to that one of the fluidpressures: ofi each; con.- troL device, whose variationsarezin; theproper direction.

The aboveand other objects are effected. by my invention, asiwill beapparent from jthetollowingdescription and claimstaken in connectionwith the accompanying, drawing forming apart of. this application inwhich:

The single: figure is, a. diagrammatic view of the control mechanismapplied toja, multiistage fluid turbine.

Referring now to the drawing more in detail, I- show an elastic, fluidturbine 10 having a-casing 11 and a rotor 12. Theturbine is suppliedwith motive fluid, which may be am suitable elastic fluid such as steamfrom a conduit 13 and the admission thereofto the turbine is controlledby an admission valve The turbine 10 is designed for operation inconnection with demand forel'astie fluid at;which.inotive fluidisadmitted to the ture bine. For example, elastic fluidat pressures015,125.. lbsnpersq inch and1'8 lbs. per sq. inch may: be required,-.while elastic fluid may beadmittedito the turbine, at a pressure of 400.lbs-ipersq. inch; Theexpansion from the latter-pressure to either. ofthe lower pressures is utilized in the turbine to develop power.

The casing: 11; is formedwith an opening 15,- ,at: anintermediate-pressure stage 155 iirom which; elastic fluid. at thehigher extraction pressure may be withdrawn .from. the turbinetwat-conduit 1-6.- It is formedw-ith-a: similar opening. 1!7 at a lower,intermediate-pressure stage 17 from which elastic fluid of lowerextraction pressuremay be withdrawn to a. conduit-.18., The openingsand.17 divide the; turbine; into at highrpressure section. 19,anlintenmediatapressure section 21 and alow, pressunesection22,theintermediate-pressure stages .15, and, 1&7.receivingpartially exp and.- ed motive fluid from the discharge orlowpressure'ends ofthe high-pressuresection19 andthe-.intermediatepressure section 21, re-s spectively.

A, diaphragm 23. isprovided between, the pressure;- stage 15 and thesection. 21,.and a I diaphragm 24:. is; provided between. the pres-'.sune sta-gel'? and. the section,22.. A passage 25-prouides a by-passaround the diaphragm, 23, and contains a valve 2,6.for controlling. theflow. o'f motivefluid. to. theintermediate pressuresectiort 2,1.Likewise,sa passage 27 providesaby pass around. the diaphragm 24;,and: avalve 28iis interposed in the passage tofcon:

trot theflow oi motive fluidto. the low pres sune section 22:. s I

It is-the-fiunction ofthevalves26v and 28 to maintain the desiredpressures atthe-pressure stages. 15,- and 147:; and the correspondingopenings L5 andl'h by holding backfromthe lower stages: the amount; oimotive fluid. res quinedi for'extractien'. In; order to-maintain.the'pressur'es; at the; extraction; stages and the speed 025 theturbinesubstantially constant, the action of these- VaILVQS and the admission talv'el l, upon changes-.in load and demands for "extracted fluid, shouldbe as follows Assume first, constant demands and flow-S:

14 and decreased openings of the valves 26 and 28. The increased amountof motive fluid held back by the valve 26 and the increased admission bythe valve 14 provide the increased amount of extracted fluid. The valve28 decreases the admission to the low-pressure section 22 by an amountequal to the decrease in flow through the intermediate-pressure section21, so that the amount of fluid for extraction through the opening 17remains the same. A portion of the power development is transferred fromthe intermediate-pressure section 21 and the low-pressure section 22 tothe high-pressure section 19. 7

Assume now constant load and constant demand at the opening 15, and anncrease in demand for fluid at the lower extraction pressure. Theopenings of the valves 14 and 26 should be increased and the opening ofthe valve 28 should be decreased. The increased flow through thehigh-presslure section 19 and the intermediate-pressuresection 21 andthe increased amount held back by the valve 28 provide the increasedamount of fluid for 8X4 traction, and a portion of the power developmentof the low-pressure section 22 is transferred to the highepressuresection 19 and the intermediate-pressure section 21.

In other words, as the demand for extracted fluid increases at any oneopening, the valves on the high-pressure side thereof should be moved inopening direction, while the valves on the low-pressure side thereofshould be moved in closing direction.

Such operation of the valves is effected by my novel control mechanismwhich will now be described. The valves 14, 26 and 28 are connected tofluid pressure governors 29, 31, and 32, respectively. Each governorincludes a cylinder 33, and a piston 34 operat-' ing therein andconnected to the associated valve through a lever 35 pivoted to astationary fulcrum at 36. A spring 37 biases the piston 34 in thedirection for opening the associated valve.

Fluid pressure varying as the square of the speed of the turbine isdeveloped by an impeller 38 mounted on the rotor shaft 39. It isconveyed through a conduit 41 to the cylinder 33' of each governor andimposed on the piston 34 in opposition to the spring 37 and in thedirection for closing the associated valve.

form of governor may be employed, and that it may embody a fluidpressure relay mechanism. Two forms of suitable constructionare shown inthe patent of O. N. Bryant, Patent No. 1,778,004, granted October 7,1930.

I11 order to modify the action of the several governors in accordancewith the variations in demand for extracted fluid, I apply an op dicatedat 43, 44, and 45, respectively. The

compensators include pressure relief valves 46, 47, and 48,respectively, communicating with the governors through conduits 49, 51,and 52.

Each compensator further. includes a plurality of pressure-responsiveelements 53, there being one such element for each opening. The elements53 bias the pressure relief valves in closing direction, and eachelement is connected thereto by a lever 54 hearing on a knife edgefulcrum 55. The fulcrum 55 is mounted on a stationary supporting plate56 and is secured thereto by a screw 57 passing through a longitudinalslot 58 in the supporting plate. The fulcrum may be moved longitudinallyof the lever to vary the lever arm ratio.

The compensators are controlled by control devices 59 and 61, associatedwith the openings 15 and 17, respectively. Each control device providestwo fluid pressures which vary in opposite directions to each other uponvariation in pressure at the associated opening; that is, one of thefluid pressures increases and the other decreases upon increase inpressure at the opening, while the first decreases and the otherincreases upon decrease in pressure at the opening.

The control device 59 includes a lever 62 pivoted to a fulcrum 63, thelatter being vertically adjustable to vary the setting of the controldevice. A diaphragm 64 is connected to the lever 62, and is subjected tothe pressure of the fluid in the conduit 16, which is communicated tothe diaphragm through a conduit 65. A spring 60 biases the lever 62 inopposition to the force of the pressure on the diaphragm 64.

The control device 59 further includes relief valves 66 and 67 which arebiased to It is to be understood that any suitable closed position bysprings 68 and 69, the latter being compression springs interposedbetween the relief valves and spring-holding mam- 74, respectively, eachof which is supplied with a restricted flow offluid under pressure froma branch: oi? the: conduit ALL-through The control device 61! is of thesame con- -s struction as: the control dGVICB' 59,, and thecorresponding parts thereof bear" the same" reference numerals with theprime'mark added. The di-apln'agm. 64 is; subjected to the pressure inthe: conduitlS, communicated thereto: through a conduit 65/. V

The pressure relief valves 66 and 67 con trolthe escape of fl-ui d' fromconduits-76 and. 77 which are alsosupplied through orifices Lwith arestricted flow oi? ii'ui'd under'presi sure from the branch oitheiconduit 412.

The flluid pressure provided by each of the reliet valves 66' 66 variesin the saline direction as the fluid: pressure imposed on the associateddiaphragmg. while the pressure provided by" the corresponding valve 6 7?or 6'2 varies at the same. time in the opposite direction. may be termedthe firsufluid pressure and the other the second fluid: pressure-,- andfor the purpose oft-he present description, the form-- or is designatedthe first fluid pressure and the latter the second: fluid pressure; I

Each or. the compensators is: subjected to the first fluid pressure ofthe control device or devices associated with opening or openings on thehigh-pressu-re' sidfe 02E the valvecontrolled' by the" compensator, andto the second fluid pressureiof any control de-' vice or devicesassociated with an opening or openings on: the low-pressure side oi thevalve controlledby'the compensator;

Accordingly. the second. fluid! pressuresof botlr control: devices are:communicated through; the conduits 74* and '27 v to the"pressure-responsive elements of the compensator l the openings 15 and1'5 being on: the lowpressure'side of theadmissionval ve' 14; One of thepressure responsive elements of the compensatortet is subjected to thefirst fluid pressure of the control device 59" communi cated throughthecondilit 7 3; since: the opening' 15* associated with the controldevice" 59- is onthe highrpressure orup-st'ream side of the valve 26,and the other pressure respone sive element is subjected tothesecondfluid pressure of the control device 61 communicated throughthe conduit 7 7; since tlieopen? ing 1? associated with the control?device 61 is on thelow-pressure or down-stream side of the valve 26s Thecompensator 45 is: con

trolled by the first fluidpressurescom-municatedl throughthe conduits- 7and? 76; as both pressures side of the: valve 28:.

Either of these. fluid pressures ,ThE -OPGI'BJtiOH of-theabove-described mcchail-ism! is as follows;

Assume, first, a change in load on the turbine withthe extractionpressures remaining constant. providing constant opposing fluidpressures thegovernors; If the load is decreased, thespeed' increases,and the increased impeller pressure acts on the piston 34 of eachgovernor tomove the associated valve in closing direction The flow toeach o-ii the sections 19,21, and 22 is decreased by alike amount,the-difference in flow between the"high-prcss-ure section and theintermechate pressuresectlon 21-,wh1ch is suppliedto the openingl5,,rema1n-1-ng constant and the d-iiferen'ce betweenthe flow throughthe-interi mediate-pressuresection Ql-and the low-pressure SGClZlQITQQJVhiClIlS sir olied to thee I en- I The resultingdecreasedin'ipellcr pressure permits the spring 37' of each governor to move thepiston: 34: in vwl-We-opening-direction. An increase in flow throughoutall the sections of the-turbine is provided to carry the increased load,the: flow through each openinga'gain remaining thesame.

Assume; now, a' condition of constant demand-forextracted fluid at thelower extraction pressure, and an increase in demand for. extractedfluid at, the higher extraction pressure at the'openinglh', theloadremaining constant. The increase demand for the higher-- pressureextracted fluid is accompaniedbya decrease in pressure thereof, whichdecrease: pressure is communicated through the conduit 65- to thediaphragm 64. The lever is rocked in clockwise direction by the spring60* an amount determined by the scaleoii the spring, and the scaleeflectof the springs 68 and 69. The compression of the spring 68 is decreased,while the compressioni ofthe spring 69 is increased, resulting indecreased first fluid pressure in the corn duit 7 3 and. increasedsecond: fluidpressure inzthe conduit 74:: 1

The. decrease in first fluid pressure of the control device- 59 reducesthe closing force on: the valves 4:7 and 418 of the compensators 44 and45 so that said valves effect decrease inthe: opposing fluid" pressuresin. the governors 31 and The impeller pressure in the governors 3 1 and32 now preponderates, and the. pistons 34: thereot movethe by-passvalves 26 in closing direction.

In response to the increased second fluid pressure provided by thecontrol device 59, thecompensator, 43 provides increased opposingpressure in the governor 29, and the latterthereupon moves the admissionvalve 14' in opening direction;

The additional motive fluid held back by the valve 28 andthe additionalmotive fluid admitted by the admission valve 14 supplies the additional:high-pressure extracted fluid to the opening 15.- The decrease in powerdevelopment in the intermediate pressure 21* p and the low-pressuresection 22, is balanced "2 19 is decreased, and the flow through theintcrmediate-pressure section 21 and the'lowpressure section 22 isincreased.

Assume, now, an increase in demand for low-pressure extracted fluid,with the demand for high-pressure extracted fluid and the load on theturbine remaining constant. The pressure of the fluid flowing throughthe opening 17 and the conduit 18 decreases,

which decrease is communicated through the conduit 65 to the diaphragm64. The lever (32' is rocked in clockwise direction by the spring acorresponding amount providing decreased first fluid pressure in theconduit 76 and increased second fluid pressure in 'the conduit 7 7 Thecompensators 43 and 44 act in response to the increase in second flu1dpressure to provide increased opposed fluid pressures in the governors29 and 31, and the latter eifect increased opening of the admissionvalve 14 'rection.

and the by-pass valve 26. The compensator 45 responds to the decreasedfirstfluldpressure by providing'decreased opposing fluld pressure in thegovernor 32, and the latter eflects closing movement of the bypass valve28. V

The increased openings of the valves 14 and 26 are such as to provideequal increases in flow through the high-pressure section 19 and theintermediate-pressure section 21.

This increased flow, together with the additional steam held back by thevalve 28, supplies the increased demand for low pressure extractedfluid. Said increase in flow is so related to the steam held back by thevalve 28 that the decrease in power development by the low-pressuresection 22 is balanced by the increase in power development by thehighpressure section 19 and the intermediatepressure section 21. V v

Upon decrease in demand for low-pressure extracted fluid, the pressurethereof increases and the parts each move in the'opposite di- The flowthrough the high-pressure section 19 and the intermediate-pressuresection 21 is decreased, and the flow through the low-pressure section22 is increased. The decrease in power development by the first twosections is balanced byjthe' increase in ,diaphragm 64 or 64.

power development by the low-pressure section 22.

The proper proportion of valve movement of the various valves inresponse to a change in pressure at one of the openings is obtained byadjusting the position of each knife edge fulcrum 55 to provide theproper lever arm ratios of the lever 54 which contacts therewith. It isto be understood that suitable well known forms of adjustment may beused throughout the control mechanism.

It will be apparent that the pressure within the region enclosed by anextraction pressure stage and the opening and extraction conduitcommunicatingtherewith is substantially the same, or at least variessimilarly with changes in demand, andthat the pressure for controllingthe associated pressureresponsive diaphragm may be taken at any pointwithin that region.

Either or both of the openings 15 or 17 may be utilized to admit motivefluid of suitable pressure to the corresponding stages instead ofextracting fluid therefrom. The operation of the parts is exactly thesame, although possibly the pressure setting. might be slightly changedby varying the vertical position of the fulcrum 53 or 53.

Assuming admission of motive fluid of suitable pressure to either of theopenings, an increase .in supply is accomplished by anincrease inpressure imposed on the corresponding The operation is the same as abovedescribed, the valves on the low-pressure side ofthe opening being movedin opening direction in order to utilize the additional supply ofrelatively low-pressure :motive fluid, and the valves on thehigh-pressure side of the opening being moved in 010s ing direction tocompensate for the increased power development on the low-pressure sideof the opening. A decrease in supply is accomplished by an increase ofpressure, and

' the valves on the low-presure side .move in closing direction whilethe valves on the high-pressure side move in opening direction.

While I have shown my invention in but one form, it will be obvious tothose skilled in the art that it is not so limited, but is susceptibleof various changes and modifications, without departing from the spiritthereof and I desire, therefore, that only such limitations shall beplaced thereupon as are imposed by the prior art or as are specificallyset forth in the appended claims.

What I claim is 1. The combination with a multi-stage prime mover havingopenings communicating with a plurality of pressure stages there in, andadmission valve for controlling the admission of motive fluid to theprime mover and a valve controlling the flow at each opening, of acontrol mechanism comprising a device associated with each opening andproviding a fluid pressure varying in one direction and another fluidpressure varying in the opposite direction in response to change inpressure at the associated opening, and a means for controlling eachvalve in response to one of the fluid pressures of each of said devices.

2. The combination with a multi-stage prime mover having openingscommunicating with a plurality of pressure stages therein, an admissionvalve for controlling the admission of motive fluid to the prime moverand a valve controlling the flow at each open ing, of a controlmechanism comprising a device associated with each opening and providinga fluid pressure varying in one direction and a second fluid pressurevarying in the opposite direction in response to change in pressure atthe associated opening, means providing a third fluid pressure varyingas a function of the speed of the prime mover, and means for controllingeach valve in response to the third fluid pressure and one of the fluidpressures of each of said devices.

3. The combination with a multi-stage elastic fluid prime mover havingopenings communicating with a plurality of pressure intermediate stagestherein, an admission valve and a valve controlling the flow at eachopening, of a control mechanism comprising a device associated with eachopening and providing a fluid pressure varying in one direction and asecond fluid pressure varying in the opposite direction in response tochange in pressure at the opening, means providing a third fluidpressure varying in response to change in speed of the prime mover, andmeans for controlling each valve comprising means providing a fourthfluid pressure varying in response to one of the fluid pressures of eachof said devices and a governor responsive to the fourth fluid pressureand to the third fluid pressure for controlling the valve.

4. The combination with a multi-stage elastic fluid prime mover havingopenings communicating with a plurality of pressure stages therein, anadmission valve for controlling the admission of motive fluid to theprime mover and a valve controlling the flow at each opening, of acontrol mechanism comprising a device associated with each. opening andproviding a first fluid pressure varying in a given direction and asecond fluid pressure varying in the opposite direction in response tochange in a given direction in pressure at the opening, and means forcontrolling each valve in response to the first fluid pressure of eachdevice at an opening on the high pressure side of the valve and to thesecond fluid pressure of each device at an opening on the low pressureside of the valve.

5. The combination with a multi-stage elastic fluid prime mover havingopenings communicating with a plurality of pressure stages therein, anadmission valve and a valve controlling the flow at each opening, of

a control mechanism comprising a device associated with each opening andproviding a first fluid pressure varying in a given direction and asecond fluid pressure varying in the opposite direction in response tochange in a given direction in the pressure at the opening, meansproviding a third fluid pressure varying in response to change in speedof the prime mover, and means for controlling each valve comprisingmeans providing a fourth fluid pressure varying in response to the firstfluid pressure of each device at an opening on the high pressure side ofthe valve and to the second fluid pressure of each device at an openingon the low pressure side of the valve and a governor responsive to thefourth fluid pressure and to the third fluid pressure for controllingthe valve.

In testimony whereof, I have hereunto subscribed my name this 3rd day ofJuly, 1930.

CLARENCE B. CAMPBELL.

